1. Field of the Invention
The present invention relates to an optical printer device that forms color images by converting electrical signals to color optical signals.
2. Description of the Related Art
A video printer is a printer that prints images, which have been digitally processed and which are shown on a display, on a sheet. Known printing methods, which are adopted for video printers, include the thermal method, inkjet method, laser-beam scanning method and the liquid-crystal shutter method. Among such methods, the liquid-crystal shutter method is suitable for the purposes of obtaining a very small and lightweight device.
An optical printer device having a liquid-crystal shutter according to prior art is described below using FIGS. 7 to 9.
As shown in FIG. 7, a light-source unit for this video printer comprises a pair of members 32, which are each arranged facing one another at a predetermined interval in a horizontal direction (the X-Y direction in FIG. 7). A support member 31 is suspended between these members 32 such that the upper end of the hollow portion, which is formed between members 32, is occupied by this support member 31.
The lengthwise direction of support member 31 (a direction perpendicular to the surface of the paper of FIG. 7) corresponds to the direction of a single line on a photosensitive member 16. A plurality of light-emitting elements are arranged on the lower face of support member 31. Light-emitting diodes (hereinafter referred to as LEDs) are used for these light-emitting elements. These light-emitting elements (LEDs) are described hereinbelow by referring to FIG. 8.
As shown in FIG. 8, an R light (red light) LED 30R, B light (blue light) LED 30B and G light (green light) LED 30G are provided close to one another in a direction (X-Y direction) that is orthogonal to the single-line direction of photosensitive material 16. Light-emitting element groups 33 are constituted by these LEDs 30R, 30G, 30B, which are aligned to form one row in the X-Y direction of FIG. 8. A plurality of light-emitting element groups 33 are arranged at a predetermined pitch (normally on the order of about 3 mm) in the single-line direction of photosensitive material 16 (a direction perpendicular to X-Y of FIG. 8).
As shown in FIG. 7, a cylindrical lens 34 is mounted at the lower end of the above-mentioned hollow portion that is formed by the pair of members 32. Further, below this cylindrical lens 34, a liquid-crystal optical shutter array 36 is provided as a optical shutter array.
Next, control of liquid-crystal optical shutter array 36 will be described using FIG. 9. For the sake of convenience in the description, the single line of photosensitive material 16 will be considered to correspond to one pixel column that comprises five pixels. Consequently, one liquid-crystal cell column of liquid-crystal shutter array 36 comprises five liquid-crystal cells. This liquid-crystal array 36 comprises four liquid-crystal cell columns arranged in a direction that is orthogonal (in the X-Y direction) to the single-line direction of these liquid-crystal cell columns. In other words, liquid-crystal shutter array 36 comprises twenty liquid-crystal cells, which are arranged in five columns and four rows. Hereinbelow, a liquid-crystal cell in column i (i=1 to 5) and row j (j=1 to 4) is represented by 36SRij. Further, in FIG. 9, liquid-crystal cells 36Sij, through which R light, which is emitted from LED30R, is transmitted, are distinguished using oblique lines.
When transportation of photosensitive material 16 begins such that the first single line is exposed, as shown in FIG. 9(a), liquid-crystal cells 36S41, 36S43, 36S45, which are in the fourth liquid-crystal cell column (liquid-crystal cells 36S41 to 36S45), are open (pattern P1). Then, after this line exposure using G light and B light is complete, same having been emitted from LEDs 30G and 30B, respectively, a transport roller (not shown in the figure) is driven to transport photosensitive material 16 by a distance of one line in the X direction of FIG. 9.
Then, when photosensitive material 16 is exposed by R light, which is emitted for a second time from LED30R, as shown in FIG. 9(b), liquid-crystal cells 36S31, 36S33, 36S35 in the third liquid-crystal cell column (liquid-crystal cells 36S31 to 36S35) are open on the basis of a pattern P1, and liquid-crystal cells 36S42, 36S44 in the fourth liquid-crystal cell column are open on the basis of a pattern P2.
As described hereinabove, in the above-mentioned technique, R-light LEDs, B-light LEDs and G-light LEDs on support member 31 are each fixed in a predetermined column and predetermined row. As a result, when displacement occurs, of the positions of R light, B light and G light on photosensitive material 16, from these predetermined positions, since no adjustment is possible of the corresponding mount positions of R-light LEDs, B-light LEDs and G-light LEDs on support member 31, positions of R light, B light and G light cannot be matched with these predetermined positions.
In addition, due to the fact that exposure of photosensitive material 16 is performed one line at a time, there is a problem in that the image-formation speed is low.
In accordance with an aspect of the present invention, an optical printer of the present invention has an exposure device which makes relative movement in a predetermined direction with respect to a photosensitive body.
The exposure device comprises a first mounting substrate for mounting a plurality of first light-emitting elements which emit light of a first color, a second mounting substrate for mounting a plurality of second light-emitting elements which emit light of a second color, and a third mounting substrate for mounting a plurality of third light-emitting elements which emit light of a third color, in addition to a frame.
The exposure device further comprises an optical shutter which controls the passage of the light from the first, second and third light-emitting elements to change the amount of irradiation onto the photosensitive body.
The first, second and third mounting substrates are configured independent of one another, respectively, and are attached to the frame.